The present invention relates generally to maintaining power output from a DC-DC converter system during an interruption of input power. More particularly, the invention relates to storing energy within the converter system and releasing the stored energy to maintain output power during interruption of input power.
In modern power supplies, two critical parameters which play a major role are the efficiency and size of the power supply. Power supply engineers have to optimize the power supply such that it achieves maximum efficiency in minimum area on a circuit board. One major parameter which affects the area of the power supply is the size of an energy storage element for a holdup feature.
Hold up time or transparency time is a critical factor in the power supply designs for aero applications. Hold up time refers to the time or interval during which there is a loss of input power to the power supply. The power supply performance should not be degraded when the equipment is subjected to power cuts shorter than its transparency time.
A typical hold up time for power supplies, used in Aerospace applications, could vary from 3 milliseconds (mS) to 200 mS based on the application or the circuitry to which the DC-DC converter may be connected. Typically, the holdup time of 200 mS would call for huge energy storage capacitors in the range of hundreds-thousands of micro farads if the capacitor were charged at a voltage equivalent to the nominal input voltage of the power supply. In some prior art power supplies, filtered input voltage is boosted to a level higher than the nominal input voltage and then fed to charge a capacitor bank. Due to the boosted charging voltage, the amount of capacitance required to provide the suitable holdup time is reduced.
While such systems may reduce the amount of capacitance required, they may subject a main converter to the high boosted voltage at its input terminals. As a consequence, such a converter may need to be constructed with components that can tolerate exposure to the high boosted voltage.
As can be seen, there is a need for an efficient system and method to provide extended hold-up time for a DC-DC converter of a power supply. More particularly, there is a need for such a system and method that provides such hold-up time without subjecting the main converter to voltages higher than nominal converter input voltages.